Cam lock burr hole plug for securing stimulation lead

ABSTRACT

A burr hole plug comprises a plug base configured for being mounted around a cranial burr hole. The plug base includes an aperture through which an elongated medical device exiting the burr hole may pass. The burr hole plug further comprises a retainer configured for being mounted within the aperture of the plug base. The retainer includes a retainer support, a slot formed in the retainer support for receiving the medical device, and a clamping mechanism having a movable clamping element and a cam configured for being rotated relative to the retainer support to linearly translate the movable clamping element into the slot, thereby securing the medical device. The retainer further comprises another clamping mechanism having another movable clamping element and another cam configured for being rotated relative to the retainer support to linearly translate the other movable clamping element, thereby laterally securing the retainer within the plug base.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/179,521, filed Jul. 24, 2008, now issued as U.S. Pat. No. 8,425,534,which application was filed concurrently with U.S. patent applicationSer. No. 12/179,525, now issued as U.S. Pat. No. 8,043,304, thedisclosures of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present inventions relate to apparatus for securing elongatedmedical devices, such as catheters or leads, within a cranial burr hole.

BACKGROUND OF THE INVENTION

Deep brain stimulation (DBS) and other related procedures involvingimplantation of electrical stimulation leads within the brain of apatient are increasingly used to treat disorders, such as Parkinson'sdisease, dystonia, essential tremor, seizure disorders, obesity,depression, restoration of motor control, and other debilitatingdiseases via electrical stimulation via stimulation of one or moretarget sites, including the ventrolateral thalamus, internal segment ofglobus pallidus, substantia nigra pars reticulate, subthalamic nucleus(STN), or external segment of globus pallidus. DBS has become aprominent treatment option for many disorders, because it is a safe,reversible alternative to lesioning. For example, DBS is the mostfrequently performed surgical disorder for the treatment of advancedParkinson's Disease. There have been approximately 30,000 patientsworld-wide that have undergone DBS surgery. Consequently, there is alarge population of patients who will benefit from advances in DBStreatment options.

During DBS procedures, at least one burr hole is meticulously cutthrough the patient's cranium as not to damage the brain tissue below, alarge stereotactic targeting apparatus is mounted to the patient'scranium, and a cannula is scrupulously positioned towards the targetsite in the brain. A stimulation lead is then introduced through thecannula, through the burr hole, and into the parenchyma of the brain,such that one or more electrodes located on the lead are strategicallyplaced at a target site in the brain of the patient. Typically, animaging device, such as a magnetic resonant imager (MRI), will be usedto visualize the lead relative to the target site. Once the lead isproperly positioned, the portion of the lead exiting the burr hole issubcutaneously routed underneath the patient's scalp to an implantablepulse generator (IPG) implanted in the patient at a site remote from theburr hole (e.g., the patient's shoulder or chest region). Furtherdetails discussing the treatment of diseases using DBS are disclosed inU.S. Pat. Nos. 6,845,267, 6,845,267, and 6,950,707, which is expresslyincorporated herein by reference.

Significantly, it is crucial that proper location and maintenance of thelead position be accomplished in order to continuously achieveefficacious therapy. This is especially so with DBS applications, inwhich cases, the target site (or sites) that is intended for electricalstimulation is about the size of a pea and is located deep within thepatient's brain. Thus, lead displacements of less than a millimeter mayhave a deleterious effect on the patient's therapy. Therefore, it isimportant that the electrode(s) of the lead be accurately located at thetarget site and that such electrode(s) be securely maintained at thetarget site during and after implantation of the lead.

To address these issues, a cranial burr hole plug is installed withinthe burr hole during the implantation procedure to hold the stimulationlead in place, as well as to seal the burr hole. Typically, the burrhole plug is composed of a multitude of components, including aring-shaped base and a retainer that are integrated together to form theburr hole plug. Optionally, a cap may be further integrated with thebase and retainer.

In particular, before the stimulation lead is introduced through theburr hole, the ring-shaped plug base is centered about the burr holeusing a special centering tool that is disposed through the plug baseinto the burr hole, and is then permanently mounted to the patient'scranium using conventional means, such as bone screws. The stimulationlead is then introduced through the plug base and into the parenchyma ofthe brain. Notably, any displacement of the portion of the lead exitingthe burr hole will result in the translation of the electrodespositioned in the brain relative to the target site, thereby requiringthe lead to be repositioned—a time consuming process.

Thus, once the lead is properly located at the tissue site, the retaineris installed within the plug base (typically in an interferencearrangement, such as a snap-fit arrangement) to secure the lead, therebypreventing migration of the lead relative to the target site duringsubsequent manipulation of the lead and installation of the optionalcap. In one exemplary embodiment, the retainer comprises a disk having aslot for receiving the lead and a clamping mechanism that can be rotatedwithin the slot towards a mating surface on the disk to frictionallyclamp the received lead therebetween. The clamping mechanism may haveone or more locking mechanisms that can engage or disengagecomplementary locking mechanisms on the disk to prevent rotation of theclamping mechanism. The portion of the stimulation lead exiting theretainer can then be bent downward towards the plane of the disk into arecess formed in the plug base, and the optional cap can be installedonto the plug base over the retainer to permanently secure the leadwithin the recess, as well as to seal the burr hole. Alternatively,instead of a cap, a biocompatible glue or other suitable adhesive can beused to seal the burr hole.

It can thus be appreciated from the foregoing that the burr hole plugserves as the platform for the entire DBS system, and therefore, it isimportant for this component to be robust, well-designed, and easy touse. Importantly, the burr hole plug should be designed, such that leadmigration is minimized during installation of the burr hole plug. Whileprior art burr hole plugs have proven to be useful in the DBS context,there are still improvements that can be made.

For example, due mostly to their flexible nature and ability to lock inonly one position, the clamping mechanisms of prior art burr hole plugsare not designed to firmly retain stimulation leads. As such, thestimulation lead may still inadvertently move even when it is supposedlysecured by the clamping mechanism. Also, because these clampingmechanisms have only one set position when clamping down on astimulation lead, prior art burr hole plugs are designed to be used withstimulation leads having one size. That is, the dimension between theretaining surface of the clamping device and the mating surface of thedisk when the clamping device is in the locked position is designed tobe slightly less than the diameter of the lead. If the diameter of theactual lead used with the burr hole plug is smaller than this intendeddiameter, the retention force applied to the lead by the clampingmechanism will not be sufficient. In contrast, if the diameter of theactual lead used with the burr hole plug is greater than this intendeddiameter, too much force will need to be applied to the lead in order toplace the clamping mechanism within the locking position, therebypotentially damaging the retainer.

As another example of a problem suffered from prior art burr hole plugs,the retainer may rotate within the plug base, potentially resulting inthe inadvertent movement of the stimulation lead from the target site.Such rotation of the retainer may typically occur in response to themanipulation of the clamping mechanism, and in particular, a downwardforce applied to the clamping mechanism that causes partialdisengagement between the retaining disk to which the clamping mechanismis mounted and the plug base, and a lateral force applied to theclamping mechanism that causes the disengaged disk to rotate within theplug base.

As yet another example, once the plug base is mounted to the patient'scranium via bone screws, it is difficult to adjust the position of theplug base when desired. Also, due to the relatively large size of thestereotactic targeting apparatus, there is often little working spaceavailable between the targeting apparatus and the burr hole to securethe stimulation and to anchor the plug base to the cranium of thepatient.

There, thus, remains a need for a burr hole plug that includes animproved means for securing a stimulation lead, for affixing theretainer to the plug base of the burr hole plug, and to anchor the burrhole plug within the burr hole formed in the cranium of a patient.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present inventions, a cranialburr hole plug is provided. The burr hole plug comprises a plug baseconfigured for being mounted around a cranial burr hole. The plug baseincludes an aperture (e.g., a circular aperture) through which anelongated medical device exiting the burr hole may pass.

The greatest dimension of the aperture may be, e.g., in the range of 10mm-20 mm. In one embodiment, the burr hole plug further comprisesfasteners configured for anchoring the plug base to a cranium of apatient. In another embodiment, the plug base comprises an inner annularflange configured for being disposed inside the cranial burr hole and anouter annular flange configured for being disposed outside of thecranial burr hole.

The burr hole plug further comprises a retainer configured for beingmounted within the aperture of the plug base. In one embodiment, theretainer is removably mounted within the plug base aperture, although inother embodiments, the retainer is formed with, or otherwise permanentlymounted to, the plug base. In another embodiment, the retainer includesat least one inner annular ledge configured for supporting the retainerwhen mounted within the plug base aperture.

The retainer further includes a retainer support, a slot formed in theretainer support for receiving the medical device (e.g., an open slotconfigured for laterally receiving the medical device), and a clampingmechanism having a movable clamping element and a cam configured forbeing rotated relative to the retainer support to linearly translate themovable clamping element into the slot, thereby securing the medicaldevice. While the present inventions should not be so limited in theirbroadest aspects, the use of a cam provides a mechanical advantage forsecuring the medical device and provides a variable clamping force thatcan secure differently sized medical devices. In one embodiment, theretainer support includes a housing that contains the clampingmechanism. In this case, the retainer may further comprise a lidconfigured for being mounted to the housing to enclose the clampingmechanism. The housing may have a sidewall and an opening within thesidewall through which the movable clamping element is configured forlinearly translating into the slot.

The retainer support may have a fixed clamping element on one side ofthe slot opposite the movable clamping element, such that the movableclamping element is configured for clamping the medical lead against thefixed clamping element. In one embodiment, the clamping mechanismfurther comprises a shaft rotatably mounted to the retainer support, inwhich case, the cam may be fixably disposed to the shaft. The shaft andcam may be eccentrically disposed relative to each other, and the shaftmay be configured for receiving a tool for rotating the shaft. In thismanner, the stimulation lead can be easily secured even when the spaceis quite limited by the stereotactic targeting apparatus. In anotherembodiment, the movable clamping element comprises a clamping flangeconfigured for engaging the medical device and a cam follower elementwith which the cam slidably engages. The cam follower element may, e.g.,be a collar circumferentially surrounding the cam.

In an optional embodiment, the cam is configured for being rotatedrelative to the retainer support to linearly translate the movableclamping element out of the slot, thereby releasing the medical device.In another optional embodiment, the retainer comprises another clampingmechanism having another movable clamping element and another camconfigured for being rotated relative to the retainer support tolinearly translate the other movable clamping element, thereby laterallysecuring the retainer within the plug base or securing the plug basewithin the cranial burr hole.

In accordance with a second aspect of the present inventions, anothercranial burr hole plug is provided. The burr hole plug comprises a plugbase configured for being mounted within a cranial burr hole. Thegreatest dimension of the aperture may be, e.g., in the range of 10mm-20 mm. The cranial burr hole further comprises a slot formed in theplug base for receiving the medical device (e.g., an open slotconfigured for laterally receiving the medical device). The burr holeplug further comprises a clamping mechanism having a movable clampingelement and a cam configured for being rotated relative to the plug baseto linearly translate the movable clamping element into the slot,thereby securing the medical device. In one embodiment, the burr holeplug further comprises a lid configured for being mounted to the plugbase to enclose the clamping mechanism. The plug base may have asidewall extending along the slot and an opening within the sidewallthrough which the movable clamping element is configured for linearlytranslating into the slot.

The plug base may have a fixed clamping element on one side of the slotopposite the movable clamping element, such that the movable clampingelement is configured for clamping the medical lead against the fixedclamping element. In one embodiment, the clamping mechanism furthercomprises a shaft rotatably mounted to the plug base, in which case, thecam may be fixably disposed to the shaft. The details of the shaft, cam,and movable clamping element can be the same as those described above.

In an optional embodiment, the cam is configured for being rotatedrelative to the plug base to linearly translate the movable clampingelement out of the slot, thereby releasing the medical device. Inanother optional embodiment, the plug base has an annular wallconfigured for being disposed within the cranial burr hole and anopening formed within the annular wall, in which case, the burr holeplug may further comprise another clamping mechanism having anothermovable clamping element and another cam configured for being rotatedrelative to the retainer support to linearly translate the other movableclamping element through the opening, thereby securing the plug basewithin the cranial burr hole.

In accordance with a third aspect of the present inventions, stillanother cranial burr hole plug is provided. The burr hole plug comprisesa plug base configured for being mounted around a cranial burr hole. Theplug base includes an aperture (e.g., a circular aperture) through whichan elongated medical device exiting the burr hole may pass. The greatestdimension of the aperture may be, e.g., in the range of 10 mm-20 mm. Inone embodiment, the burr hole plug further comprises fastenersconfigured for anchoring the plug base to a cranium of a patient. Inanother embodiment, the plug base comprises an inner annular flangeconfigured for being disposed inside the cranial burr hole and an outerannular flange configured for being disposed outside of the cranial burrhole.

The burr hole plug further comprises a retainer configured for beingmounted within the aperture of the plug base. In one embodiment, theretainer is removably mounted within the plug base aperture, although inother embodiments, the retainer is formed with, or otherwise permanentlymounted to, the plug base. In another embodiment, the retainer includesat least one inner annular ledge configured for supporting the retainerwhen mounted within the plug base aperture.

The retainer further includes a retainer support, a slot formed in theretainer support for receiving the medical device (e.g., an open slotconfigured for laterally receiving the medical device), and a clampingmechanism having a movable clamping element and a cam configured forbeing rotated relative to the retainer support to linearly translate themovable clamping element towards the plug base, thereby laterallysecuring the retainer within the plug base. While the present inventionsshould not be so limited in their broadest aspects, the use of a camprovides a convenient, efficient, and robust means for securing theretainer to the plug base. In one embodiment, the retainer supportincludes a housing that contains the clamping mechanism. In this case,the retainer may further comprise a lid configured for being mounted tothe housing to enclose the clamping mechanism. The housing may have asidewall and an opening within the sidewall through which the movableclamping element is configured for linearly translating towards the plugbase. In another embodiment, the plug base comprises an inner annularflange configured for engaging the movable clamping element whenlinearly translated through the opening within the sidewall, therebyaxially securing the retainer within the plug base.

In one embodiment, the clamping mechanism further comprises a shaftrotatably mounted to the retainer support, in which case, the cam may befixably disposed to the shaft. The shaft and cam may be eccentricallydisposed relative to each other, and the shaft may be configured forreceiving a tool for rotating the shaft. In this manner, the retainercan be easily secured to the plug base even when the space is quitelimited by the stereotactic targeting apparatus. In another embodiment,the movable clamping element comprises a clamping flange configured forengaging the plug base and a cam follower element with which the camslidably engages. The cam follower element may, e.g., be a collarcircumferentially surrounding the cam.

In an optional embodiment, the cam is configured for being rotatedrelative to the retainer support to linearly translate the movableclamping element away from the plug base, thereby releasing the retainerfrom the plug base. In another optional embodiment, the retainercomprises another clamping mechanism having another movable clampingelement and another cam configured for being rotated relative to theretainer support to linearly translate the other movable clampingelement, thereby laterally securing the medical device.

In accordance with a fourth aspect of the present inventions, yetanother cranial burr hole plug is provided. The burr hole plug comprisesa plug base having an annular sidewall configured for being mountedwithin a cranial burr hole and an opening formed through the annularsidewall. The greatest dimension of the aperture may be, e.g., in therange of 10 mm-20 mm. The cranial burr hole further comprises a slotformed in the plug base for receiving the medical device (e.g., an openslot configured for laterally receiving the medical device). The burrhole plug further comprises a clamping mechanism having a movableclamping element and a cam configured for being rotated relative to theplug base to linearly translate the movable clamping element through theopening in the annular sidewall, thereby securing the plug base to thecranial burr hole. While the present inventions should not be so limitedin their broadest aspects, the use of a cam provides a means forreversibly anchoring the plug base within a burr hole. In oneembodiment, the burr hole plug further comprises a lid configured forbeing mounted to the plug base to enclose the clamping mechanism. In oneembodiment, the clamping mechanism further comprises a shaft rotatablymounted to the plug base, in which case, the cam may be fixably disposedto the shaft. The details of the shaft, cam, and movable clampingelement can be the same as those described above.

In an optional embodiment, the cam is configured for being rotatedrelative to the plug base to linearly translate the movable clampingelement inward through the opening in the sidewall, thereby releasingthe plug base from the cranial burr hole. In another optionalembodiment, the retainer comprises another clamping mechanism havinganother movable clamping element and another cam configured for beingrotated relative to the plug base to linearly translate the othermovable clamping element, thereby securing the medical device. In thiscase, the plug base may have a sidewall extending along the slot and anopening within the sidewall through which the other movable clampingelement is configured for linearly translating into the slot.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of a Deep Brain Stimulation (DBS) system implantedwithin a patient;

FIG. 2 is an exploded view of a burr hole plug constructed in accordancewith one embodiment of the present inventions;

FIG. 3 is a top perspective view of the burr hole plug of FIG. 2;

FIG. 4 is a bottom perspective view of the burr hole plug of FIG. 2,particularly showing stimulation lead and plug base clamping mechanismsin their fully recessed positions;

FIG. 5 is a bottom perspective view of the burr hole plug of FIG. 2,particularly showing stimulation lead and plug base clamping mechanismsin their fully deployed positions;

FIG. 6 is a top view of the burr hole plug of FIG. 2, particularlyshowing the stimulation lead clamping mechanism in its fully recessedposition;

FIG. 7 is a bottom view of the burr hole plug of FIG. 2, particularlyshowing the stimulation lead clamping mechanism in its fully recessedposition and the plug base clamping mechanism in its fully deployedposition;

FIG. 8 is a side view of the burr hole plug of FIG. 2;

FIG. 9 is a cross-sectional perspective view of the burr hole plug ofFIG. 2, particularly showing stimulation lead and plug base clampingmechanisms in their fully recessed positions;

FIG. 10 is a cross-sectional perspective view of the burr hole plug ofFIG. 2, particularly showing stimulation lead and plug base clampingmechanisms in their fully deployed positions;

FIG. 11 is a top perspective view of a plug base used in the burr holeplug of FIG. 2;

FIG. 12 is a bottom perspective view of a plug base used in the burrhole plug of FIG. 2;

FIG. 13 is an exploded view of a retainer used in the burr hole plug ofFIG. 2;

FIG. 14 is a top perspective view of the retainer of FIG. 13;

FIG. 15 is a bottom perspective view of the retainer of FIG. 13;

FIG. 16 is a top perspective view of the retainer of FIG. 14 with thelid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully recessed positions;

FIG. 17 is a top perspective view of the retainer of FIG. 14 with thelid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully deployed positions;

FIG. 18 is another top perspective view of the retainer of FIG. 14 withthe lid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully recessed positions;

FIG. 19 is another top perspective view of the retainer of FIG. 14 withthe lid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully deployed positions;

FIG. 20 is a top view of the retainer of FIG. 14 with the lid removed,particularly showing the stimulation lead and plug base clampingmechanisms in their fully recessed positions;

FIG. 21 is a top view of the retainer of FIG. 14 with the lid removed,particularly showing the stimulation lead and plug base clampingmechanisms in their fully deployed positions;

FIG. 22 is a top perspective view of a retainer support used in theretainer of FIG. 14;

FIG. 23 is a bottom perspective view of a retainer support used in theretainer of FIG. 14;

FIG. 24 is a close-up view of the lid-locking recesses and lid pop-outrecesses formed in the retainer support of FIG. 22;

FIG. 25 is an exploded view of another retainer that can be used in theburr hole plug of FIG. 2;

FIG. 26 is a top perspective view of the retainer of FIG. 25;

FIG. 27 is a bottom perspective view of the retainer of FIG. 25;

FIG. 28 is a top perspective view of the retainer of FIG. 25 with thelid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully recessed positions;

FIG. 29 is a top perspective view of the retainer of FIG. 25 with thelid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully deployed positions;

FIG. 30 is another top perspective view of the retainer of FIG. 25 withthe lid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully recessed positions;

FIG. 31 is another top perspective view of the retainer of FIG. 25 withthe lid removed, particularly showing the stimulation lead and plug baseclamping mechanisms in their fully deployed positions;

FIG. 32 is a top view of the retainer of FIG. 25 with the lid removed,particularly showing the stimulation lead and plug base clampingmechanisms in their fully recessed positions;

FIG. 33 is a top view of the retainer of FIG. 25 with the lid removed,particularly showing the stimulation lead and plug base clampingmechanisms in their fully deployed positions;

FIG. 34 is a top perspective view of a retainer support used in theretainer of FIG. 25;

FIG. 35 is a bottom perspective view of a retainer support used in theretainer of FIG. 25;

FIG. 36 is an exploded view of a burr hole plug constructed inaccordance with another embodiment of the present inventions;

FIG. 37 is a top perspective view of the burr hole plug of FIG. 36;

FIG. 38 is a bottom perspective view of the burr hole plug of FIG. 36,particularly showing stimulation lead and burr hole clamping mechanismsin their fully recessed positions;

FIG. 39 is a bottom perspective view of the burr hole plug of FIG. 36,particularly showing stimulation lead and burr hole clamping mechanismsin their fully deployed positions;

FIG. 40 is a top view of the burr hole plug of FIG. 36, particularlyshowing the stimulation lead clamping mechanism in its fully recessedposition;

FIG. 41 is a bottom view of the burr hole plug of FIG. 36, particularlyshowing the stimulation lead and burr hole clamping mechanisms in theirfully deployed positions;

FIG. 42 is a side view of the burr hole plug of FIG. 36, particularlyshowing the burr hole clamping mechanism in its fully recessed position;

FIG. 43 is a side view of the burr hole plug of FIG. 36, particularlyshowing the burr hole clamping mechanism in its fully deployed position;

FIG. 44 is a top perspective view of the burr hole plug of FIG. 36 withthe lid removed, particularly showing the stimulation lead and burr holeclamping mechanisms in their fully recessed positions;

FIG. 45 is a top perspective view of the burr hole plug of FIG. 36 withthe lid removed, particularly showing the stimulation lead and burr holeclamping mechanisms in their fully deployed positions;

FIG. 46 is a top view of the burr hole plug of FIG. 36 with the lidremoved, particularly showing the stimulation lead and burr holeclamping mechanisms in their fully recessed positions;

FIG. 47 is a top view of the burr hole plug of FIG. 36 with the lidremoved, particularly showing the stimulation lead and burr holeclamping mechanisms in their fully deployed positions;

FIG. 48 is a top perspective view of a plug base used in the burr holeplug of FIG. 36; and

FIG. 49 is a bottom perspective view of a plug base used in the burrhole plug of FIG. 36.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Turning first to FIG. 1, an exemplary DBS system 10 constructed inaccordance with one embodiment of the present inventions is shownimplanted within a patient for the treatment of a debilitating diseasesuch as, Parkinson's disease, dystonia, essential tremor, seizuredisorders, obesity, depression, etc. The system 10 comprises astimulation lead 12 implanted within the parenchyma of the brain 2 of apatient 1 in order to position electrodes 14 carried by the distal endof the stimulation lead 12 adjacent a target tissue region 3, such as adeep brain structure of the patient (e.g., the ventrolateral thalamus,internal segment of globus pallidus, substantia nigra pars reticulate,subthalamic nucleus, or external segment of globus pallidus). Thus,electrical stimulation energy can be conveyed from the electrodes 14 tothe target tissue region 3 to treat the disease. As can be seen, thestimulation lead 12 is introduced into the head 4 of the patient 1 via aburr hole 5 formed in the cranium 6 of the patient 1. In alternativeembodiments, multiple stimulation leads (not shown) may be used, all ofwhich may be located within the head 4 of the patient 1 via the sameburr hole 5.

To secure the stimulation lead 12 (or leads), the system 10 furthercomprises a burr hole plug 16 mounted to the cranium 6 around the burrhole 5 of the patient 1. The stimulation lead 12 extends from the burrhole 5, through the burr hole plug 16, to a location external to thecranium 6. Details discussing the structure and function of variousembodiments of the burr hole plug 16 will be discussed in further detailbelow.

The DBS system 10 further comprises a neurostimulator 17, such as animplantable pulse generator (IPG), radio frequency (RF)receiver-stimulator, or any other device coupled to and capable ofdelivering electrical stimulation energy to the stimulation lead 12 in acontrolled and therapeutic manner. The neurostimulator 17 may begenerally implanted in a surgically-made pocket in the torso of thepatient (e.g., the chest or shoulder region). The neurostimulator 17may, of course, also be implanted in other locations of the patient'sbody. The DBS system 10 further comprises a lead extension 19, which maybe suitably connected to the proximal end of the stimulation lead 12 andsubcutaneously advanced underneath the scalp 7 of the patient 1 to theneurostimulator implantation site, thereby facilitating the location ofthe neurostimulator 17 away from the exit point of the stimulation lead12 (i.e., the burr hole 5). In alternative embodiments, theneurostimulator 17 may be directly implanted on or within the cranium 6of the patient 1, as described in U.S. Pat. No. 6,920,359, which isexpressly incorporated herein by reference. In this case, the leadextension 19 may not be needed. After implantation, the neurostimulator17 is used to provide the therapeutic stimulation under control of thepatient 1. The system 10 may include external components, such as apatient handheld programmer, a clinician programming station, and anexternal charger (all not shown), the details of which will not bedescribed herein for purposes of brevity.

In should be understood that, while the invention lends itself well toapplications in DBS, the invention, in its broadest aspects, may not beso limited. For example, the stimulation lead 12 (or leads) can bedelivered within regions of the brain other than a deep brain structure,e.g., within or on the surface of the cerebral cortex. In addition,electrical leads, other than stimulation leads, may be delivered withinthe head 4 of the patient 1. For example, an electrical recording leadcan be delivered into the head 4 of the patient 1 via the burr hole 5 tosense brain signals, either alone or in conjunction with a stimulationlead. Further, elongated medical devices other than electrical leads;for example, drug delivery catheters or needles, may be delivered intothe head 4 of the patient 1 via the burr hole 5. Thus, it can beappreciated that the burr hole plugs described herein can be used withany elongated medical device intended to be delivered through a burrhole 5 within the cranium 6 of a patient 1 for any therapeutic and/ordiagnostic purpose.

Referring now to FIGS. 2-10, one embodiment of the burr hole plug 16will be described. The burr hole plug 16 generally comprises a plug base(or shell) 18 configured for being fixably mounted about a burr hole,and a retainer 20 configured for being mounted within the plug base 18to secure a stimulation lead extending through the burr hole. Anoptional cap (not shown) can be mounted to the plug base 18 over theretainer 20 in order to further secure the stimulation lead 12 (orleads). The burr hole plug 16 further comprises a plurality of fasteners(not shown) for mounting the plug base 18 to the cranium of the patient.Any of the components of the burr hole plug 16 may be composed of asuitable hard biocompatible material, such as titanium, stainless steel(e.g., MP35N), alloys, or hard polymers (e.g., a high durometersilicone, polyurethane, or polyethertheterketone (PEEK)).

Referring further to FIGS. 11 and 12, the plug base 18 includes a closedring-shaped body 24 and an aperture 26 through which the stimulationlead exiting from the burr hole may pass. The profile of the ring-shapedbody 24 is preferably minimized as much as possible, such that the plugbase 18 does not noticeably protrude from the cranium underneath thescalp of the patient. To this end, the plug base 18 conventionallycomprises an inner cylindrical flange 28 configured for being disposedwithin the cranial burr hole, and an outer circular flange 30orthogonally extending radially outward from the top of the inner flange28, such that the outer flange 30 is configured to reside outside of thecranial burr hole on top of the cranium when the inner flange 28 isdisposed within the cranial burr hole. As a result, the height of theprofile of the burr hole plug 16 above the cranial burr hole is equal tothe thickness of the outer flange 30 (as best shown in FIG. 8), therebyreducing the visibility of the burr hole plug 16 below the patient'sscalp. The size of the inner flange 28 preferably matches the size ofthe cranial burr hole, such that an outer surface 32 of the inner flange28 firmly engages the cranial burr hole. In this case, the greatestdimension (in this case, its diameter) of the inner flange 28 may be inthe range of 10 mm-20 mm. The bottom surface 34 of the ring-shaped body24 may optionally be concave (not shown) in order to match the curvatureof a typical cranium.

In the illustrated embodiment, the plug base 18 is permanently anchoredto the cranium of the patient. To this end, the plug base 18 includesthree fastening holes 36 formed within the outer flange 30 of thering-shaped body 24 for respectively receiving anchoring fasteners (notshown), such as, e.g., screws, pins, spikes, tabs, or buttons.Alternatively, other means of anchoring the plug base 18 to the craniumof the patient, such as, e.g., adhesion, can be used. Relief structures(not shown) may be added to the bottom surface 34 of the ring-shapedbody 24 and the outer surface 32 of the inner flange 28 to preventrotational movement between the plug base 18 and the burr hole prior topermanent anchoring to the cranium. Such relief structures may include,e.g., a rough sandpaper-like surface, notches, bumps, horizontal orvertical ribs or threads, etc.

The plug base 18 also comprises an inner annular ledge 38 configured forsupporting the retainer 20 when mounted within the plug base aperture26. In particular, the annular ledge 38 is disposed on the inner surface40 of the inner flange 28, thereby preventing the retainer 20 fromdescending too far into the burr hole when mounted within the aperture26. The plug base 18 further comprises an annular ridge 42 extendingradially inward from the inner surface 40 of the inner flange 28 justbelow the annular ledge 38. As will be described in further detailbelow, the annular ridge 42 allows the retainer 20 to be axially securedwithin the plug base aperture 26. In the illustrated embodiment, thering-shaped body 24 is closed, thereby maximizing the durability of theplug base 18. In one alternative embodiment, the plug base 18 mayinclude an open slot (not shown) configured for laterally receiving thestimulation lead. This permits the plug base 18 to be mounted to thecranium around the burr hole after the stimulation lead has beeninserted through the burr hole and into the brain tissue by simplysliding the stimulation lead through the slot as the plug base 18 ismoved into place. In another alternative embodiment, the plug base 18may comprise at least two body portions (not shown) that can beintegrated together when mounting to the burr hole.

Referring further to FIGS. 13-24, the details of the retainer 20 willnow be described. As clearly shown in FIG. 13, the retainer 20 comprisesa retainer support 44 configured for being mounted within the plug baseaperture 26 (shown in FIGS. 11 and 12), a lead clamping mechanism 46mounted to the retainer support 44 and configured for securing thestimulation lead, a base clamping mechanism 48 mounted to the retainersupport 44 and configured for securing the retainer 20 within the plugbase 18, and a lid 50 configured for containing the clamping mechanisms46, 48 within the retainer support 44.

As best shown in FIGS. 22 and 23, the retainer support 44 comprises adisk-shaped housing 52 having an outer annular or cylindrical sidewall54, a bottom floor 56, and a cavity 58 in which the clamping mechanisms46, 48 are disposed. The retainer support 44 further comprises an openlead slot 60 formed in the retainer housing 52 for laterally receivingthe stimulation lead, thereby allowing the retainer 20 to be mountedwithin the plug base aperture 26 after the stimulation lead has beenintroduced through the burr hole. In the illustrated embodiment, thelead slot 60 radially extends through the center of the retainer housing52. The lead slot 60 may alternatively terminate at or short of thecenter of the retainer housing 52 or may be offset from the center ofthe retainer housing 52. The retainer housing 52 further comprises aninner U-shaped sidewall 62 that extends around the lead slot 60. Inparticular, the inner sidewall 62 has two straight sidewall portions 64,66 that extend along opposite sides of the lead slot 60, and a curvedsidewall portion 68 that connects the straight sidewall portions 64, 66at the end of the lead slot 60.

The retainer support 44 further comprises a first opening 70 formed inone of the straight sidewall portions 64, 66 and a second opening 72formed in the outer sidewall 54. As will be described in further detailbelow, the first and second openings 70, 72 respectively accommodatemovement of the lead and base clamping mechanisms 46, 48. The retainersupport 44 further comprises first and second holes 74, 76 formedthrough the bottom floor 56 of the retainer housing 52 to which certainelements of the lead and base clamping mechanisms 46, 48 are mounted, aswill also be described in further detail below.

The retainer support 44 further comprises an annular lip 78 formed atthe top of, and extending radially outward from the outer surface 80 of,the outer sidewall 54. Thus, as best shown in FIGS. 9 and 10, when theretainer 20 is mounted within the plug base 18, the lower surface of theannular lip 78 (also shown in FIGS. 14 and 15) rests on the uppersurface of the annular ledge 38 (also shown in FIG. 11) formed on theinner surface 40 of the inner plug base flange 28, thereby restrainingaxial movement of the retainer 20 into the cranial burr hole. In thisconfiguration, the top of the retainer 20 is preferably flush with thetop of the plug base 18. The retainer support 44 also comprises anannular recess 82 that circumferentially extends around a portion of theouter surface 80 of the outer sidewall 54 just below the annular lip 78.As will be described in further detail below, the annular recess 82(also shown in FIG. 14) receives the annular ridge 42 located on theinner surface 40 of the inner plug base flange 28 to axially secure theretainer 20 within the plug base 18. In the illustrated embodiment, theannular recess 82 circumferentially extends 180 degrees around the outersidewall 54. As best shown in FIGS. 5, 9, and 10, an annular aperture 84is formed between the outer sidewall 54 of the retainer housing 52 andthe inner flange 28 of the plug base 18 when the retainer 20 is mountedwithin the plug base 18. In this manner, the retainer 20 may freely spinwithin the plug base 18 until the base clamping mechanism 48 isactuated, as will be described in further detail below.

The retainer support 44 is configured for receiving the lid 50 in aninterference arrangement, and in particular, a snap-fit arrangement. Tothis end, the retainer support 44 further comprises a plurality of lidlocking recesses 86 (as best shown in FIG. 24) formed in the innersurface 88 of the outer sidewall 54. As will be described in furtherdetail below, the lid locking recesses 86 can receive corresponding lidlocking ridges (described below) for facilitating mounting of the lid 50to the retainer housing 52. Alternatively, the lid 50 can be secured tothe retainer housing 52 using a threaded arrangement or bonding means,such as heat welding. The retainer support 44 further comprises aplurality of tab-like ledges 90 extending along the bottom floor 56 fromthe outer sidewall 54 and the inner sidewall 62. Each of the ledges 90has a height that is flush with the lid locking recesses 86, such thatthe ledges 90 prevent the movement of the lid 50 past the lid lockingrecesses 86, thereby facilitating mounting of the lid 50 onto theretainer housing 52. The retainer support 44 further comprises aplurality of corresponding lid pop-out recesses 92 (as best shown inFIG. 24) located at a top inner edge 94 of the outer sidewall 54 suchthat a tool (not shown) can be inserted into one of the lid pop-outrecesses 92 to remove the previously mounted lid 50 from the retainerhousing 52.

As best shown in FIG. 13, the lid 50 comprises a disk-shaped flange 96having a diameter substantially equal to the inner diameter of the outersidewall 54 of the retainer housing 52. The lid 50 further comprises aslot 97 formed within the disk-shaped flange 96 that accommodates theinner sidewall 62 of the retainer housing 52 (shown in FIG. 22), and aplurality of ridges 98 (in this case four) equally spaced around theedge of the disk-shaped flange 96 for being received within the lidlocking recesses 86 formed around the inner surface 88 of the outersidewall 54 of the retainer housing 52 (shown in FIG. 24). The lid 50further comprises first and second holes 100, 102 formed through thedisk-shaped flange 96 for providing access to the clamping mechanisms46, 48, as will be described in further detail below.

Referring specifically to FIGS. 16-21, the lead clamping mechanism 46comprises a movable clamping element 104 slidably disposed on the bottomfloor 56 of the retainer housing 52, a cam 106 slidably engaged with themovable clamping element 104, and a cam shaft 108 on which the cam 106is affixed. The cam shaft 108 is rotatably mounted within the first hole74 formed in the bottom floor 56 of the retainer housing 52, such thatit can be rotated about a fixed axis to rotate the cam 106 relative tothe retainer support 44. The end of the cam shaft 108 includes a toolengagement element 110 for engaging a tool (not shown) that can providea mechanical advantage for rotation of the cam 106. In the illustratedembodiment, the tool engagement element 110 is hexagonal recess, therebyallowing rotation of the cam 106 using an Allen wrench. Other types oftool engagement elements, such as a slotted recess for receiving a flathead screwdriver, a crossed recess for receiving a Phillips screwdriver,or a bolt head for receiving an open-ended wrench, box-end wrench, orsocket wrench can also be used. The location of the first hole 74 in thebottom floor 56 of the retainer housing 52 corresponds to the first hole100 in the lid 50 (shown in FIG. 13), such that the end of the cam shaft108 is seated within the first hole 100 to provide access to the toolengagement element 110.

The movable clamping element 104 comprises a clamping flange 112configured for engaging the medical device, and a cam follower element114 with which the cam 106 slidably engages. The cam 106 and cam shaft108 are in an eccentric relationship, such that rotation of the camshaft 108 about the fixed axis (i.e., the axis extending through thefirst hole 74) rotates the cam 106, which in turn, linearly translatesthe clamping flange 112 through the inner sidewall opening 70 and intothe lead slot 60 as the cam 106 slidably engages the cam followerelement 114. In the illustrated embodiment, the movable clamping element104 can be displaced from a fully recessed position (FIGS. 4, 16, 18,and 20) to a fully deployed position (FIGS. 5, 17, 19, and 21) byrotating the cam shaft 108, and thus the cam 106, over an angle of 180degrees from its initial angular position. However, other angular rangescan be used to displace the movable clamping element 104 between thefully recessed position and the fully deployed position. In theillustrated embodiment, the cam 106 is circular, although in alternativeembodiments, can be other shapes, including oval or oblong.

In the illustrated embodiment, the clamping flange 112 includes twohorizontal and parallel ridges 116 that facilitate retention of thestimulation lead. The movable clamping element 104 may be composed of ahigh friction material, such as a high durometer silicone orpolyurethane, to maximize lead retention. The straight sidewall portion64 on the other side of the lead slot 60 serves as a fixed clampingelement with which the movable clamping element 104 cooperates to securethe stimulation lead therebetween. To ensure that the movable clampingelement 104 smoothly slides out into the lead slot 60 without rotating,the width of the clamping flange 112 is slightly less than the width ofthe inner sidewall opening 70, such that the sides of the clampingflange 112 slidably engage the edges of the inner sidewall opening 70.The movable clamping element 104 further comprises a pair of opposinglimiting tabs 118 outwardly extending away from the cam follower element114. These limiting tabs 118 will abut the straight sidewall portion 66to limit movement of the clamping element 104 through the inner sidewallopening 70, thereby preventing the clamping element 104 from fallinginto the lead slot 60.

The lead clamping mechanism 46 may include one or more spring elements(not shown) that urge the clamping element 104 back into its fullyrecessed position when the cam 106 is rotated to its initial position(i.e., 0 degree rotation). Alternatively, the lead clamping mechanism 46may incorporate a ratchet feature or a one-way clutch feature (notshown) between the cam 106 and the cam follower element 114 to preventloosening/slippage of the clamping element 104. An override feature,such as a push-button release (not shown) can be incorporated to allowthe clamping element 104 to release the stimulation lead.

The base clamping mechanism 48 is similar to the lead clamping mechanism46 in that it comprises a movable clamping element 124 slidably disposedon the bottom floor 56 of the retainer housing 52, a cam 126 slidablyengaged with the movable clamping element 124, and a cam shaft 128 onwhich the cam 126 is affixed. The cam shaft 128 is rotatably mountedwithin the second hole 76 formed in the bottom floor 56 of the retainerhousing 52, such that it can be rotated about a fixed axis to rotate thecam 126 relative to the retainer support 44. The end of the cam shaft128 includes a tool engagement element 130 for engaging a tool (notshown) that can provide a mechanical advantage for rotation of the cam126. In the illustrated embodiment, the tool engagement element 130 ishexagonal recess, thereby allowing rotation of the cam 126 using anAllen wrench. Other types of tool engagement elements, such as a slottedrecess for receiving a flat head screwdriver, a crossed recess forreceiving a Phillips screwdriver, or a bolt head for receiving anopen-ended wrench, box-end wrench, or socket wrench can also be used.The location of the second hole 76 in the bottom floor 56 of theretainer housing 52 corresponds to the second hole 102 in the lid 50(shown in FIG. 13), such that the end of the cam shaft 128 is seatedwithin the second hole 102 to provide access to the tool engagementelement 130.

The movable clamping element 124 comprises a clamping flange 132configured for engaging the inner flange 28 of the plug base 18, and acam follower element 134 with which the cam 126 slidably engages. Thecam 126 and cam shaft 128 are in an eccentric relationship, such thatrotation of the cam shaft 128 about the fixed axis (i.e., the axisextending through the second hole 76) rotates the cam 126, which inturn, linearly translates the clamping flange 132 through the outersidewall opening 72 and into the annular space 84 (shown in FIGS. 5, 7,9, and 10) formed between the retainer housing 52 and the inner flange28 of the plug base 18 as the cam 126 slidably engages the cam followerelement 134. In the illustrated embodiment, the movable clamping element124 can be displaced from a fully recessed position (FIGS. 4, 9, 16, 18,and 20) to a fully deployed position (FIGS. 5, 10, 17, 19, and 21) byrotating the cam shaft 128, and thus the cam 126, over an angle of 180degrees from its initial angular position. However, other angular rangescan be used to displace the movable clamping element 124 between thefully recessed position and the fully deployed position. In theillustrated embodiment, the cam 126 is circular, although in alternativeembodiments, can be other shapes, including oval or oblong.

Notably, as best shown in FIG. 9, the upper surface of the clampingflange 132 slidably engages the lower surface of the annular ridge 42formed on the inner flange 28 of the plug base 18, which in conjunctionwith the engagement between the annular recess 82 on the outer surface80 of the outer sidewall 54 of the retainer housing 52 and the annularridge 42 opposite the outer sidewall opening 72, prevents axial movementbetween the plug base 18 and the retainer 20. In the illustratedembodiment, the clamping flange 132 has an annular surface having aradius of curvature that matches the radius of curvature of the innersurface 40 of the inner flange 28 of the plug base 18, therebymaximizing contact, and thus the clamping force, between the clampingflange 132 and the plug base 18. The movable clamping element 124 may becomposed of a high friction material, such as a high durometer siliconeor polyurethane, to further maximize the clamping force applied to theplug base 18.

To ensure that the movable clamping element 124 smoothly slides out intothe annular space 84 between the outer sidewall 54 of the retainerhousing 52 and the inner flange 28 of the plug base 18, the width of theclamping flange 132 is slightly less than the width of the outersidewall opening 72, such that the sides of the clamping flange 132slidably engage the edges of the outer sidewall opening 72. The movableclamping element 104 further comprises a pair of opposing limiting tabs138 outwardly extending away from the cam follower element 134. Theselimiting tabs 138 will abut the inner surface of the outer sidewall 54to limit movement of the clamping element 124 through the outer sidewallopening 72, thereby preventing the clamping element 124 from fallinginto the annular space 84.

The base clamping mechanism 48 may include one or more spring elements(not shown) that urge the clamping element 124 back into its fullyrecessed position when the cam 126 is rotated to its initial position(i.e., 0 degree rotation). Alternatively, the base clamping mechanism 48may incorporate a ratchet feature or a one-way clutch feature (notshown) between the cam 126 and the cam follower element 134 to preventloosening/slippage of the clamping element 124. An override feature,such as a push-button release (not shown) can be incorporated to allowthe clamping element 124 to release the stimulation lead.

Referring now to FIGS. 25-35, an alternative embodiment of a retainer220 that can be mounted within the plug base 18 will be described. Theretainer 220 is similar to the retainer 20, with the exception that itcomprises a retainer housing 252 with an inner J-shaped sidewall 262(instead of an inner U-shaped sidewall) that extends along one side of,and wraps around the end of, the lead slot 60, as shown in FIG. 34.Thus, the lead slot 60 is completely open to the cavity 58 within theretainer housing 252. The retainer 220 also comprises a lid 250 that issimilar to the lid 50, with the exception that it comprises a slot 297that accommodates the inner J-shaped sidewall 262 of the retainerhousing 252, as shown in FIG. 25. The retainer 220 also comprises a leadclamping mechanism 246 and a base clamping mechanism 248 that arerespectively similar to the lead clamping mechanism 46 and base clampingmechanism 48, with the exception that they are respectively configuredfor being actuated to additionally release the stimulation lead and theplug base 18.

In particular, and with specific reference to FIGS. 28-33, instead ofhaving a pair of limiting tabs, the lead clamping mechanism 246 includesa cam follower element 314 in the shape of a collar that surrounds thecam 106. The cam follower element 314 is oblong or oval-shaped, and isoriented, such that an imaginary line drawn through its smallestdimension is perpendicular to the lead slot 60. In this manner, the cam106 is capable of slidably engaging the opposite portions of the camfollower element 314 that are coincident with the imaginary line. Thus,rotation of the cam shaft 108 in one direction rotates the cam 106,which in turn, linearly translates the clamping flange 112 into the leadslot 60 as the cam 106 slidably engages the portion of the cam followerelement 314 closest to the lead slot 60. Continued rotation of the camshaft 108 in the same direction or rotation of the cam shaft 108 in theopposite direction, rotates the cam 106, which in turn, linearlytranslates the clamping flange 112 away from the lead slot 60 as the cam106 slidably engages the portion of the cam follower element 314furthest from the lead slot 60. Thus, the movable clamping element 104can be displaced from a fully recessed position (FIGS. 28, 30, and 32)to a fully deployed position (FIGS. 29, 31, and 32) by rotating the camshaft 108, and thus the cam 106, over an angle of 180 degrees from itsinitial position, and then displaced back to the fully recessed positionby rotating the cam shaft 108, and thus the cam 106, back to its initialposition.

Similarly, instead of having a pair of limiting tabs, the base clampingmechanism 248 includes a cam follower element 334 in the shape of acollar that surrounds the cam 126. The cam follower element 334 isoblong or oval-shaped, and is oriented, such that an imaginary linedrawn through its smallest dimension is perpendicular to the outersidewall opening 72. In this manner, the cam 126 is capable of slidablyengaging the opposite portions of the cam follower element 334 that arecoincident with the imaginary line. Thus, rotation of the cam shaft 128in one direction rotates the cam 126, which in turn, linearly translatesthe clamping flange 112 through the outer sidewall opening 72 and intothe annular space (not shown) formed between the retainer housing 252and the inner flange 28 of the plug base 18 as the cam 126 slidablyengages the cam follower element slidably engages the portion of the camfollower element 334 closest to the outer sidewall opening 72. Continuedrotation of the cam shaft 128 in the same direction or rotation of thecam shaft 128 in the opposite direction, rotates the cam 126, which inturn, linearly translates the clamping flange 132 through the outersidewall opening 72 away from the annular space formed between theretainer housing 252 and the inner flange 28 of the plug base 18 as thecam 106 slidably engages the portion of the cam follower element 334furthest from the outer sidewall opening 72. Thus, the movable clampingelement 124 can be displaced from a fully recessed position (FIGS. 28,30, and 32) to a fully deployed position (FIGS. 29, 31, and 32) byrotating the cam shaft 128, and thus the cam 126, over an angle of 180degrees from its initial position, and then displaced back to the fullyrecessed position by rotating the cam shaft 128, and thus the cam 126,back to its initial position.

Referring now to FIGS. 36-49, another embodiment of a burr hole plug 416will now be described. The burr hole plug 416 differs from thepreviously described burr hole plug 16 in that it does not include aremovable retainer. Instead, the clamping mechanisms are integrateddirectly into the plug base to allow the burr hole plug 416 to beremovably secured within a burr hole, in addition to securing thestimulation lead.

To this end, and as clearly shown in FIG. 36, the burr hole plug 416generally comprises a plug base (or shell) 418 configured for beingfixably mounted about a burr hole, a lead clamping mechanism 446configured for securing a stimulation lead received into the plug base418, a burr hole clamping mechanism 448 configured for securing the plugbase 418 within the burr hole, and a lid 450 configured for containingthe clamping mechanisms 446, 448 within the plug base 418. As with theprevious burr hole plug 16, an optional cap (not shown) can be mountedto the plug base 418 in order to seal the burr hole. Notably, the burrhole plug 416 does not comprise separate fasteners, although inalternative embodiments, they can be used as an additional means forsecuring the plug base 18 to the cranium. Any of the components of theburr hole plug 416 may be composed of a suitable hard biocompatiblematerial, such as titanium, stainless steel (e.g., MP35N), alloys, orhard polymers (e.g., a high durometer silicone, polyurethane, orpolyethertheterketone (PEEK)).

As best shown in FIGS. 48 and 49, the plug base 418 includes adisk-shaped body 424 and a slot 426 formed within the plug body 424 tolaterally receive the stimulation lead. This permits the plug base 418to be mounted to the cranium around the burr hole after the stimulationlead has been inserted through the burr hole and into the brain tissueby simply sliding the stimulation lead through the slot 426 as the plugbase 418 is moved into place. Like the previous plug body 24, theprofile of the plug body 424 is preferably minimized as much aspossible, such that the plug base 418 does not noticeably protrude fromthe cranium underneath the scalp of the patient. To this end, the plugbase 424 comprises a retainer support 444 configured for being disposedwithin the cranial burr hole, and an outer circular flange 430orthogonally extending radially outward from the top of the retainersupport 444, such that the outer flange 430 is configured to resideoutside of the cranial burr hole on top of the cranium when the retainersupport 444 is disposed within the cranial burr hole. As a result, theheight of the profile of the burr hole plug 416 above the cranial burrhole is equal to the thickness of the outer flange 430 (as best shown inFIGS. 42 and 43), thereby reducing the visibility of the burr hole plug416 below the patient's scalp. The outer diameter of the retainersupport 444 preferably matches the size of the cranial burr hole, suchthat an outer surface of the retainer support 444 firmly engages thecranial burr hole. In this case, the greatest dimension (in this case,its diameter) of the retainer support 444 may be in the range of 10mm-20 mm. The bottom surface 434 of the ring-shaped body 424 mayoptionally be concave (not shown) in order to match the curvature of atypical cranium. As briefly discussed above, the plug base 418 need notbe permanently anchored to the cranium of the patient, and thus does notinclude fastening holes formed within the outer flange 430.

In many respects, the retainer support 444 is similar to the retainersupport 44 described above, with the exception that it somewhat largerin order to be firmly received within the burr hole. To this end, theretainer support 444 comprises a retainer housing 452 having an outerannular or cylindrical sidewall 454, a bottom floor 456, and a cavity458 in which the clamping mechanisms 446, 448 are disposed. Asillustrated, the lead slot 426 radially extends through the center ofthe retainer housing 452. The lead slot 426 may alternatively terminateat or short of the center of the retainer housing 452 or may be offsetfrom the center of the retainer housing 452. The retainer housing 452further comprises an inner U-shaped sidewall 462 that extends around thelead slot 426. The inner sidewall 462 has two straight sidewall portions464, 466 that extend along opposite sides of the lead slot 426, and acurved sidewall portion 468 that connects the straight sidewall portions464, 466 at the end of the lead slot 426.

The retainer support 444 further comprises a first opening 470 formed inone of the straight sidewall portions 464, 466 and a second opening 472formed in the outer sidewall 454. As will be described in further detailbelow, the first and second openings 470, 472 respectively accommodatemovement of the lead and base clamping mechanisms 446, 448. The retainersupport 444 further comprises first and second holes 474, 476 formedthrough the bottom floor 456 of the retainer housing 452 to whichcertain elements of the lead and base clamping mechanisms 446, 448 aremounted, as will also be described in further detail below.

The retainer support 444 is configured for receiving the lid 450 in aninterference arrangement, and in particular, a snap-fit arrangement. Tothis end, the retainer support 444 further comprises a plurality of lidlocking recesses 486 formed in the inner surface 488 of the outersidewall 454. As will be described in further detail below, the lidlocking recesses 486 can receive corresponding lid locking ridges(described below) for facilitating mounting of the lid 450 to theretainer housing 452. Alternatively, the lid 450 can be secured to theretainer housing 452 using a threaded arrangement or bonding means, suchas heat welding. The retainer support 444 further comprises a pluralityof tab-like ledges 490 extending along the bottom floor 456 from theouter sidewall 454 and the inner sidewall 462. Each of the ledges 490has a height that is flush with the lid locking recesses 486, such thatthe ledges 490 prevent the movement of the lid 450 past the lid lockingrecesses 486, thereby facilitating mounting of the lid 450 onto theretainer housing 452. The retainer support 444 further comprises aplurality of corresponding lid pop-out recesses 492 located at a topinner edge 494 of the outer sidewall 454 such that a tool (not shown)can be inserted into one of the lid pop-out recesses 492 to remove thepreviously mounted lid 450 from the retainer housing 452.

The lid 450 is similar to the lid 50 described above, with the exceptionthat it is somewhat larger to accommodate the larger cavity 458 of theretainer housing 452. As best shown in FIG. 36, the lid 450 furthercomprises a disk-shaped flange 496, a slot 497 formed within thedisk-shaped flange 496 that accommodates the inner sidewall 462 of theretainer housing 452, and a plurality of ridges 498 (in this case four)equally spaced around the edge of the disk-shaped flange 496 for beingreceived within the lid locking recesses 486 formed around the innersurface 488 of the outer sidewall 454 of the retainer housing 452. Thelid 450 further comprises first and second holes 500, 502 formed throughthe disk-shaped flange 496 for providing access to the clampingmechanisms 446, 448, as will be described in further detail below.

Referring specifically to FIGS. 44-47, the structure and operation ofthe lead clamping mechanism 446 is similar to that of the lead clampingmechanism 46 discussed above. In particular, the lead clamping mechanism446 comprises a movable clamping element 504 slidably disposed on thebottom floor 456 of the retainer housing 452, a cam 506 slidably engagedwith the movable clamping element 504, and a cam shaft 508 on which thecam 506 is affixed. The cam shaft 508 is rotatably mounted within thefirst hole 474 formed in the bottom floor 456 of the retainer housing452, such that it can be rotated about a fixed axis to rotate the cam506 relative to the retainer support 444. The end of the cam shaft 508includes a tool engagement element 510 for engaging a tool (not shown)that can provide a mechanical advantage for rotation of the cam 506. Thedetails of the tool engagement element 510 may be the same as those ofthe tool engagement element 110 described above. The location of thefirst hole 474 in the bottom floor 456 of the retainer housing 452corresponds to the first hole 500 in the lid 450 (shown in FIG. 36),such that the end of the cam shaft 508 is seated within the first hole500 to provide access to the tool engagement element 510.

The movable clamping element 504 comprises a clamping flange 512configured for engaging the medical device, and a cam follower element514 with which the cam 506 slidably engages. The cam 506 and cam shaft508 are in an eccentric relationship, such that rotation of the camshaft 508 about the fixed axis (i.e., the axis extending through thefirst hole 474) rotates the cam 506, which in turn, linearly translatesthe clamping flange 512 through the inner sidewall opening 440 and intothe lead slot 426 as the cam 506 slidably engages the cam followerelement 514. In the illustrated embodiment, the movable clamping element504 can be displaced from a fully recessed position (FIGS. 38, 40, 44,and 46) to a fully deployed position (FIGS. 39, 41, 45, and 47) byrotating the cam shaft 508, and thus the cam 506, over an angle of 180degrees from its initial angular position. However, other angular rangesbe used to displace the movable clamping element 504 between the fullyrecessed position and the fully deployed position. In the illustratedembodiment, the cam 506 is circular, although in alternativeembodiments, can be other shapes, including oval or oblong.

In the illustrated embodiment, the clamping flange 512 includes twohorizontal and parallel ridges 516 that facilitate retention of thestimulation lead. The movable clamping element 504 may be composed of ahigh friction material, such as a high durometer silicone orpolyurethane, to maximize lead retention. The straight sidewall portion464 on the other side of the lead slot 426 serves as a fixed clampingelement with which the movable clamping element 504 cooperates to securethe stimulation lead therebetween. To ensure that the movable clampingelement 504 smoothly slides out into the lead slot 426 without rotating,the width of the clamping flange 512 is slightly less than the width ofthe inner sidewall opening 470, such that the sides of the clampingflange 512 slidably engage the edges of the inner sidewall opening 470.The movable clamping element 504 further comprises a pair of opposinglimiting tabs 518 outwardly extending away from the cam follower element514. These limiting tabs 518 will abut the straight sidewall portion 466to limit movement of the clamping element 504 through the inner sidewallopening 470, thereby preventing the clamping element 504 from fallinginto the lead slot 426. As described above with respect to the leadclamping mechanism 46, the lead clamping mechanism 446 may include oneor more spring elements, a ratchet feature or a one-way clutch feature(not shown), and an override feature, such as a push-button release (notshown).

The structure and operation of the burr hole clamping mechanism 448 issimilar to that of the base clamping mechanism 48 discussed above. Inparticular, the burr hole clamping mechanism 448 comprises a movableclamping element 524 slidably disposed on the bottom floor 456 of theretainer housing 452, a cam 526 slidably engaged with the movableclamping element 524, and a cam shaft 528 on which the cam 526 isaffixed. The cam shaft 528 is rotatably mounted within the second hole476 formed in the bottom floor 456 of the retainer housing 452, suchthat it can be rotated about a fixed axis to rotate the cam 526 relativeto the retainer support 444. The end of the cam shaft 528 includes atool engagement element 530 for engaging a tool (not shown) that canprovide a mechanical advantage for rotation of the cam 526. The detailsof the tool engagement element 530 may be the same as those of the toolengagement element 130 described above. The location of the second hole476 in the bottom floor 456 of the retainer housing 452 corresponds tothe second hole 502 in the lid 350 (shown in FIG. 36), such that the endof the cam shaft 528 is seated within the second hole 502 to provideaccess to the tool engagement element 530.

The movable clamping element 524 comprises a clamping flange 532configured for engaging the burr hole (not shown), and a cam followerelement 534 with which the cam 526 slidably engages. The cam 526 and camshaft 528 are in an eccentric relationship, such that rotation of thecam shaft 528 about the fixed axis (i.e., the axis extending through thesecond hole 476) rotates the cam 526, which in turn, linearly translatesthe clamping flange 532 through the outer sidewall opening 472 and intoan annular space (not shown) formed between the retainer housing 452 andthe burr hole as the cam 526 slidably engages the cam follower element534. In the illustrated embodiment, the movable clamping element 524 canbe displaced from a fully recessed position (FIGS. 38, 42, 44, and 46)to a fully deployed position (FIGS. 39, 41, 43, 45, and 47) by rotatingthe cam shaft 528, and thus the cam 526, over an angle of 180 degreesfrom its initial angular position. However, other angular ranges be usedto displace the movable clamping element 524 between the fully recessedposition and the fully deployed position. In the illustrated embodiment,the cam 526 is circular, although in alternative embodiments, can beother shapes, including oval or oblong.

To ensure that the movable clamping element 524 smoothly slides out intothe annular space between the outer sidewall 454 of the retainer housing452 and the burr hole, the width of the clamping flange 532 is slightlyless than the width of the outer sidewall opening 472, such that thesides of the clamping flange 532 slidably engage the edges of the outersidewall opening 472. The movable clamping element 504 further comprisesa pair of opposing limiting tabs 538 outwardly extending away from thecam follower element 534. These limiting tabs 538 will abut the innersurface of the outer sidewall 454 to limit movement of the clampingelement 524 through the outer sidewall opening 472, thereby preventingthe clamping element 524 from falling into the annular space. Asdescribed above with respect to the retainer clamping mechanism 48, theburr hole clamping mechanism 448 may include one or more springelements, a ratchet feature or a one-way clutch feature (not shown), andan override feature, such as a push-button release (not shown).

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. A cranial burr hole plug for a medical device,comprising: a plug base configured for being mounted within a cranialburr hole; a slot formed in the plug base for receiving the medicaldevice; and a clamping mechanism having a movable clamping element and acam configured for being rotated relative to the plug base to linearlytranslate the movable clamping element into the slot, thereby securingthe medical device.
 2. The burr hole plug of claim 1, further comprisinga lid configured for being mounted to the plug base to enclose theclamping mechanism.
 3. The burr hole plug of claim 1, wherein the plugbase has a sidewall extending along the slot and an opening within thesidewall through which the movable clamping element is configured forlinearly translating into the slot.
 4. The burr hole plug of claim 1,wherein the clamping mechanism further comprises a shaft rotatablymounted to the plug base, the cam being fixably disposed to the shaft.5. The burr hole plug of claim 4, wherein the shaft and cam areeccentrically disposed relative to each other.
 6. The burr hole plug ofclaim 4, wherein the shaft is configured for receiving a tool forrotating the shaft.
 7. The burr hole plug of claim 1, wherein the cam isconfigured for being rotated relative to the plug base to linearlytranslate the movable clamping element out of the slot, therebyreleasing the medical device.
 8. The burr hole plug of claim 1, whereinthe movable clamping element comprises a clamping flange configured forengaging the medical device and a cam follower element with which thecam slidably engages.
 9. The burr hole plug of claim 8, wherein the camfollower element is a collar circumferentially surrounding the cam. 10.The burr hole plug of claim 1, wherein the slot is an open slotconfigured for laterally receiving the medical device.
 11. The burr holeplug of claim 1, wherein the plug base has a fixed clamping element onone side of the slot opposite the movable clamping element, and themovable clamping element is configured for clamping the medical leadagainst the fixed clamping element.
 12. The burr hole plug of claim 1,wherein the plug base has an annular wall configured for being disposedwithin the cranial burr hole and an opening formed within the annularwall, the burr hole plug further comprising another clamping mechanismhaving another movable clamping element and another cam configured forbeing rotated relative to the plug base to linearly translate the othermovable clamping element through the opening, thereby securing the plugbase within the cranial burr hole.